Method for heat recovery in manufacturing gasified fuel

ABSTRACT

The present invention provides a method for manufacturing a gasified fuel gasified by partial oxidation of a liquid fuel which contains water and has decreased viscosity effected by using oxygen, in which a water-decreased gasified fuel is manufactured by heating the liquid fuel to a predetermined temperature to separate into a water layer and a fuel layer, and by partially oxidizing; by using oxygen, the fuel layer obtained by liquid-liquid separation at the stage just before gasification so that gasification is carried out. The separation into a water layer and a fuel layer can be accelerated by adding an emulsion breaker to the liquid fuel or by applying an electric field.

2. FIELD OF THE INVENTION AND RELATED ART STATEMENT

[0001] The present invention relates to a method for manufacturing gasified fuel, by which a water-decreased gasified fuel is obtained from a liquid fuel which contains water and has reduced viscosity.

[0002] Also, the present invention relates to a method and apparatus for heat recovery in manufacturing gasified fuel in a process in which a gasified fuel is cooled to a temperature below the temperature at which water vapor condenses, and sulfur compounds are absorbed and separated by bringing the cooled gas into contact with an absorbent.

[0003] Conventionally, a method has been used in which a raw fuel such as coal, heavy oil, and Olimulsion is partially oxidized into gasified fuel and the gasified fuel is used as the fuel for gas turbine etc. In recent years, various new fuels have been used as raw fuels.

[0004] For example, a technology for utilizing natural tar called Olinoco tar as fuel has been developed. Olinoco tar, which is obtained at the basin of the River Olinoco in Venezuela of South America, has high viscosity in the normal state though having a sufficient heating value, exhibiting properties of super-heavy oil. As for viscosity, as shown in FIG. 2, Olinoco tar can be classified according to specific gravity (unit in the oil industry: API Baume degree), and the lower the specific gravity is, the higher the viscosity (kinematic viscosity) is. Therefore, Olinoco tar is common in that the viscosity decreases with the increase in temperature though different specific gravity gives different temperature-viscosity characteristic.

[0005] From this view point, special methods are used for extraction and transportation. For the extraction, water is poured in Olinoco tar, and water and a surface active agent are added for getting emulsion to decrease the viscosity, which enables pumping-up and transportation by pipeline etc.

[0006] An emulsion obtained by adding water (about 30%) and a surface active agent to natural Olinoco tar (about 70%) has been commercialized as Olimulsion (registered trade name of Bitumens Olinoco S.A.).

[0007] However, when a raw fuel is gasified and used as a gasified fuel, the gasification of fuel is carried out at a high temperature of several hundred degrees centigrade. Therefore, when the raw fuel contains much water or it is used by adding water, the quantity of heat for heating or evaporating a large amount of water unconcerned with the gasification is consumed wastefully, and further the size of facility increases and corrosion caused by much water and gas such as hydrogen chloride is liable to occur.

[0008] For example, natural Olinoco tar has so far been used as an emulsion, that is, tar containing water of about 30%. For this reason, water of about 14% is contained in the gas gasified by oxygen. Therefore, when the gas is cooled in removing impurities such as hydrogen sulfide in the gas, water is condensed and lost, resulting in a large heat loss. Moreover, since much water is contained in the gasified gas, sulfur content cannot be removed sufficiently by the dry gas refining method using iron oxide etc.

[0009] Also, when a raw fuel contains much water or it is used by adding water, the resultant gasified fuel has a high temperature above several hundred degrees centigrade and contains much water vapor and sulfur compounds such as hydrogen sulfide. When desulfurization is carried out by bringing the gasified fuel into contact with an absorbent of amine series, the gasified fuel must be cooled to a temperature close to the ordinary temperature to enhance the absorbing efficiency so that acid gases such as hydrogen sulfide and carbon dioxide are absorbed. For this reason, high-temperature gasified fuel is cooled by using cooling water by means of a heat exchanger, and therefore the heat of condensation generated when water vapor turns to water is thrown away to the cooling water side.

3. OBJECT AND SUMMARY OF THE INVENTION

[0010] In view of the actual situation of the above-described prior art, an object of the present invention is to provide a method for manufacturing gasified fuel, in which even a liquid fuel which contains water and has decreased viscosity can be gasified in a state in which water is removed without relying on evaporation having high energy consumption, so that a water-decreased gasified fuel can be obtained.

[0011] Another object of the present invention is to provide a method and apparatus for heat recovery in manufacturing gasified gas, in which the heat of condensation of water vapor dissipated in cooling a high-temperature gasified fuel can be recovered to the deoxidized gasified gas.

[0012] The inventors earnestly studied the methods for manufacturing gasified fuel from a liquid fuel which contains water and has decreased viscosity. As the result of the study, we found the fact that a liquid fuel which contains water and has decreased viscosity separates into a water layer and a fuel layer, and the fuel layer obtained by liquid-liquid separation is partially oxidized by oxygen to produce a gasified fuel, by which the aforementioned problems can be solved, and we completed the present invention.

[0013] The present invention provides a method for manufacturing a gasified fuel gasified by partial oxidation of a liquid fuel which contains water and has decreased viscosity effected by using oxygen, in which a water-decreased gasified fuel is manufactured by heating the liquid fuel to a predetermined temperature to separate into a water layer and a fuel layer, and by partially oxidizing, by using oxygen, the fuel layer obtained by liquid-liquid separation at the stage just before gasification so that gasification is carried out.

[0014] In the present invention, a liquid fuel which contains water and has decreased viscosity (hereinafter referred simply to as a liquid fuel) means a fuel in which a raw fuel such as crude oil, heavy oil, super-heavy oil, and oil sand is made water emulsion, having viscosity of a degree such that the fuel can be transported by a pump or burned by a burner. That is, the viscosity of this liquid fuel at ordinary temperature is 50 to 100 centipoises.

[0015] For example, Olimulsion whose viscosity is reduced by pouring water to Olinoco tar and by adding water and a surface active agent contains Olinoco tar of about 70% and water of about 30%, and its viscosity is 50 to 100 centipoises at ordinary temperature.

[0016] On the other hand, the viscosity of raw fuel (Olinoco tar) itself is as shown in FIG. 2, and the raw fuel exhibits sufficient flowability at temperatures above 100° C., preferably above 120° C. Even after water is separated, it has flowability of a degree such that it can be transported by a pump or a gasified fuel can be obtained by partially oxidizing it by a burner.

[0017] Separation of water from a liquid fuel is effected by heating the liquid fuel at a temperature above 150° C., preferably at 150 to 180° C. to separate into a water layer and a fuel layer and by effecting liquid-liquid separation by using the difference in specific gravity after being allowed to stand. Heating is effected in a pressurized state to prevent water from boiling.

[0018] Olinoco tar has different characteristics depending on its type as shown in FIG. 1 (classify according API Baume degree), but it is common in that the specific gravity (here, ordinary specific gravity) decreases significantly with the increase in temperature. On the other hand, since the specific gravity of water-does not change so much with temperature, the difference in specific gravity between Olinoco tar and water increases when the temperature of Olinoco tar increases, so that the separation becomes easy. This is clearly shown in FIG. 1 that various Olinoco tars have specific travities of about 0.970 in 100° C.

[0019] When a liquid fuel is heated, the separation into a fuel layer and a water layer can be accelerated by adding an emulsion breaker. As the emulsion breaker, when a cation or anion type surface active agent is used in the liquid fuel, the reverse ion type compound is used, and when a nonionic surface active agent is used, a compound to which alcohol, ether, fatty acid ester, ethylene glycols, silicone oil, etc. are added is used.

[0020] The separation into a water layer and a fuel layer is accelerated by applying an electric field in a heated state. The electric field can be applied in a settling vessel such as a dehydrator. The dehydrator, which is, for example, of an electrostatic type, has many electrodes in a drum-shaped vessel and separates emulsion into a fuel layer and a water layer by applying an electric field by a DC or AC voltage between these electrodes and the drum body. The principle of acceleration of water separation due to application of electric field is that the water molecule has a dipole, and when an electric field is applied to this dipole, the water molecules are arranged readily, so that they are aggregated easily. Thereby, the emulsion state is destroyed, by which the separation into Olinoco tar and water is effected.

[0021] As described above, the separation of water can be effected by heating only, by the combination of heating and an emulsion breaker, by the combination of heating and application of electric field, or by the combination of heating, an emulsion breaker, and application of electric field.

[0022] By the aforementioned separation of water, the water content in the fuel layer can be decreased usually to a value below 3%, preferably to 1.0 to 1.5%.

[0023] The gasified fuel is a gaseous fuel obtained by partially oxidizing various raw fuels in a reducing atmosphere by using oxygen (in this specification, oxygen contains oxygen-containing gas such as air) in a gasifying device. The gasified fuel contains hydrogen and carbon monoxide as main components and also contains carbon dioxide, water, nitrogen, sulfur compounds such as hydrogen sulfide and carbonyl sulfide, or ammonia, hydrogen chloride, etc. and further sometimes contains soot and dust.

[0024] In the present invention, the liquid fuel is separated into a water layer and a fuel layer at the stage just before gasification, liquid-liquid separation is effected, and only the fuel layer is gasified. The stage just before gasification means that the fuel from which water is substantially separated is used immediately in the next partial oxidation process. A strainer, a heat exchanger etc., and an agitator etc. may be interposed between the process in which separation into a water layer and a fuel layer is effected and the partial oxidation process.

[0025] The gasified fuel obtained by partial oxidation may be pressurized, be under ordinary pressure, or be decompressed, but it is obtained usually in a pressurized state of several atmospheres to several tens of atmospheres, and it contains water of about 2 to 5 vol %.

[0026] By the above-described configuration, in a state in which the fuel is heated to a high temperature just before the gasification system, water is removed by, for example, a dehydrator. Therefore, the viscosity is sufficiently low even water is removed, so that smooth supply to the gasification system is possible.

[0027] According to the present invention, even a liquid fuel to which water is added to decrease the viscosity can be partially oxidized after water is separated. Therefore, the water in the gasified gas is reduced significantly, and the facility after the partial oxidation reactor can be decreased greatly.

[0028] Also, the inventors earnestly studied the above-described problem. As a result, we found the fact that a high-temperature gasified fuel is cooled by a saturator to a temperature below the temperature at which water vapor condenses, and water is poured in the desulfurized gasified fuel and the fuel is heated by the saturator, by which the heat of condensation of water vapor dissipated in cooling is efficiently recovered to the desulfurized gasified fuel, and we completed other modes of the present invention.

[0029] A first mode of the present invention provides a heat recovery method in manufacturing gasified fuel, characterized in that a gasified fuel containing water vapor and sulfur compounds, which is obtained by partially oxidizing fuel by using oxygen, is cooled by a saturator to a temperature below the temperature at which water vapor condenses, the cooled gasified fuel is brought into contact with an absorbent and the sulfur compounds are absorbed and separated to obtain a desulfurized gasified fuel, and then water is poured in the desulfurized gasified fuel and the fuel is heated by the saturator.

[0030] A second mode of the present invention provides a heat recovery apparatus which comprises a saturator for cooling a gasified fuel containing water vapor and sulfur compounds, which is obtained by partially oxidizing fuel by using oxygen, by a saturator to a temperature below the temperature at which water vapor condenses, a desulfurizing device for bringing the cooled gasified fuel into contact with an absorbent to absorb and separate the sulfur compounds, and a cooling device before desulfurization in which water is poured in the desulfurized gasified fuel after the desulfurized gasified fuel is obtained, and in which water is poured in the desulfurized gasified fuel and the fuel is heated by the saturator.

[0031]FIG. 3 is a schematic view of a heat recovery apparatus in accordance with the present invention.

[0032] In the figure, reference numeral 1 denotes a raw fuel gasifying device. To this raw fuel gasifying device are connected a dust removing device 2, a heat exchanger 3 before reduction of carbonyl sulfide, a carbonyl sulfide reducing device 4, a saturator 5, a cooling device 6 before desulfurization, and a desulfurizing device 7 in sequence. A gas turbine 8 is connected to the heat exchanger 3 before reduction of carbonyl sulfide. The desulfurizing device 7 is also connected to the saturator 5. The cooling water from the cooling device 6 before desulfurization is supplied to the top of the saturator 5 by a pump 9. Reference numeral 11 in the figure denotes exhaust gas discharged from the gas turbine 8, 12 denotes a sulfur compound absorbent supplied to the desulfurizing device 7, 13 denotes gas such as hydrogen sulfide and carbon dioxide discharged from the desulfurizing device 7, and 14 denotes cooling water.

[0033] In the present invention, the gasified fuel is a gaseous fuel obtained by partially oxidizing a raw fuel such as crude oil, heavy oil, coal, Olimulsion, oil sand, and oil slurry in a reducing atmosphere by using air or oxygen (hereinafter both are called oxygen) in the raw fuel gasifying device 1. The gasified fuel contains hydrogen, carbon monoxide, carbon dioxide, water, nitrogen, sulfur compounds such as hydrogen sulfide and carbonyl sulfide, or ammonia, hydrogen chloride, etc. and sometimes contains oxygen and further sometimes contains soot and dust.

[0034] The gasified fuel obtained by partial oxidation has a high temperature of several hundred degrees centigrade, and may be pressurized, may be under ordinary pressure, or may be decompressed. Usually, it is obtained in a pressurized state of several atmospheres to several tens of atmospheres, and it contains water of about 2 to 20 vol %. Therefore, the temperature at which water vapor condenses is determined by water content and pressure.

[0035] The saturator 5 used in the present invention can heat-exchanging (A) high-temperature side fluid containing water vapor and (B) low-temperature side fluid containing water by a heat transfer wall in terms of sensible heat and latent heat, and the heat of condensation of water vapor in (A) is converted into the heat of evaporation of water in (B). At this time, by using the desulfurized gasified fuel as the low-temperature side fluid, energy is concentrated to one gasified fuel, so that the gasified fuel can efficiently be used for the gas turbine etc.

[0036] The type of the saturator 5 includes, for example, a tube type heat exchanger separating into a shell side and a tube side, which may be of single tube type or multiple tube type. A high-temperature gas is made to pass on the shell side, and a low-temperature gas and water are poured on the tube side, by which evaporation may be accelerated by boiling heat transfer, or the reverse case may be possible.

[0037] As the poured water, the condensed water produced when the gasified fuel is cooled in the cooling device 6 before desulfurization or the water from the outside is used, by which the energy concentration to the gasified fuel can be increased. FIG. 3 shows an example in which the condensed water is used. In this case, make-up water 25 may be supplied if necessary.

[0038] When a corrosive matter is contained in the gas before desulfurization, condensed water is produced. Therefore, the materials of devices after the saturator 5 are selected by considering corrosion. As the material, carbon steel, molybdenum steel, chrome-molybdenum steel, austenitic stainless steel, ferritic stainless steel, nickel alloys, etc. are used.

[0039] When the gasified fuel obtained by partial oxidation contains soot and dust, it is preferable that soot and dust be removed by using the dust removing device 2, for example, a cyclone, electric dust collector, and filter. Thereby, soot and dust of, for example, several ten thousand ppm can be decreased to several ppm.

[0040] When the dust-removed gasified fuel contains carbonyl sulfide, it is cooled to a suitable temperature by the heat exchanger 3 before reduction of carbonyl sulfide. In this case, cooling can preferably be effected by the desulfurized gasified fuel which has passed the saturator.

[0041] When the gasified fuel contains carbonyl sulfide, it is reduced to hydrogen sulfide in advance in the presence of catalyst in the carbonyl sulfide reducing device 4, by which sulfur compounds are removed in the subsequent desulfurizing process. As the catalyst, for example, alumina series catalyst is used.

[0042] The gasified fuel, in which dust is removed and carbonyl sulfide is reduced to hydrogen sulfide as described above, still has a high temperature of 200 to 400° C., and also has much sensible heat and latent heat due to water. Therefore, heat exchanging is performed by pouring the desulfurized gasified fuel using the saturator 5.

[0043] The gasified fuel-condensed water mixture after heat exchanging in the saturator 5 is further cooled to a temperature suitable for the desulfurizing process, for example, 60 to 30° C., by bringing it into contact with a cooled medium in the cooling device 6 before desulfurization if necessary. The cooling of the medium in the cooling device 6 before desulfurization may be effected by heat exchanging with cooling water, or can be effected by a liquid absorbing sulfur compounds. For example, the heat exchange is effected by making an absorbent flow on the shell side or the tube side and making the gasified fuel-condensed water mixture pass on the tube or shell side. Thereby, the heat of the gasified fuel-condensed water mixture after being heat exchanged in the saturator can be made heating energy when the absorbent absorbing sulfur compounds is regenerated.

[0044] The cooling may be effected at one stage, or can be effected at multiple stages.

[0045] The gasified fuel-condensed water mixture cooled to a temperature suitable for the desulfurizing process comes in contact with the absorbent in the desulfurizing device 7, by which sulfur compounds such as hydrogen sulfide is absorbed and removed. As the absorbent, for example, amine series absorbent can be used. The amine series absorbent is water soluble, and may contain water.

[0046] The absorbent absorbing sulfur compounds is regenerated by discharging acid gases such as hydrogen sulfide and carbon dioxide by heating, decompression, etc.

[0047] The desulfurized gasified fuel after being heat exchanged in the saturator, or the desulfurized gasified fuel after being heat exchanged with the gasified fuel after dust is further removed is used as a fuel for the gas turbine 8, a fuel cell, etc. after small amounts of sulfur compounds and gases such as hydrogen chloride are further removed as necessary.

[0048] The present invention can be carried out in a batch mode, semi-batch mode, or continuous mode.

[0049] As described above, according to the present invention, the heat of condensation dissipated when a gasified fuel containing much water is cooled to a temperature necessary for the desulfurizing process can be recovered efficiently.

4. BRIEF DESCRIPTION OF THE DRAWINGS

[0050]FIG. 1 is a temperature-specific gravity characteristic diagram for Olinoco tar suitable for the application to the present invention;

[0051]FIG. 2 is a temperature-viscosity characteristic diagram for Olinoco tar suitable for the application to the present invention; and

[0052]FIG. 3 is a schematic view of a heat recovery apparatus in accordance with the present invention.

5. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0053] The method of the present invention will be explained specifically by a description of working examples.

WORKING EXAMPLE 1

[0054] The case where the fuel is Olimulsion will be described below. Olimulsion (water content 29%) liquidized by mixing natural Olinoco tar of 70% with water of 30% containing small amounts of sulfonic acid type surface active agent is stored in a tank. The temperature of Olimulsion in the tank is 20 to 30° C., which is close to the ordinary temperature. This Olimulsion was pressurized to about 20 kg/cm² by a pump, and supplied to a heat exchanger. The heat source for the heat exchanger was high-temperature water removed by a later-described dehydrator, being heated to 50 to 60° C. The Olimulsion was further heated to 150° C., and the heated Olimulsion was supplied to the dehydrator and allowed to stand, by which it was separated into a fuel layer at the upper layer and a water layer at the lower layer. This was liquid-liquid separated to obtain a fuel layer containing about 2.0% water content. This fuel layer was further heated and partially oxidized by using a partial oxidation reactor. Thus, a gasified fuel containing hydrogen and carbon monoxide as main components and containing hydrocarbon, water, hydrogen sulfide, etc. was obtained.

[0055] On the other hand, the separated water was supplied to the heat exchanger as described above, treated after heat exchange, and discharged to the outside of the system.

WORKING EXAMPLE 2

[0056] A cation type emulsion breaker of an amount exceeding the equivalent amount of surface active agent was added to the Olimulsion used in the working example 1, and the Olimulsion was heated to 50° C. and agitated. It was further heated to 150° C. and supplied to the dehydrator, where it was allowed to stand and separated into a water layer and a fuel layer. The fuel layer was made to overflow and supplied to the partial oxidation reactor. The water content in the fuel layer was about 1.8%.

WORKING EXAMPLE 3

[0057] A cation type emulsion breaker of an amount exceeding the equivalent amount of surface active agent was added to the Olimulsion used in the working example 1, and the Olimulsion was heated to 50° C. and agitated. It was further heated to 120° C. in an extracting vessel and agitated by adding heavy oil. After the separation into a water layer and a fuel layer was accelerated, the Olimulsion was supplied into a precipitate separating tank. After the supernatant fuel layer was made to overflow, it was supplied into the partial oxidation reactor. The water content in the fuel layer was about 1.6%.

WORKING EXAMPLE 4

[0058] The dehydrator used in working example 2 was changed to an electrostatic type having many electrodes in a drum-shaped vessel. A 200V DC voltage was applied between these electrodes and the drum body of vessel to accelerate separation by applying an electric field. The overflowing fuel layer contained a water of 1.5%. The fuel layer was further heated to 150° C. and supplied into the partial oxidation reactor for partial oxidation, by which a gasified fuel containing hydrogen and carbon monoxide as main components and containing hydrocarbon, water and gases containing hydrogen sulfide etc. was obtained.

[0059] Table 1 gives the composition and higher heating value (wet) before gasification of raw Olimulsion and dehydrated Olimulsion obtained by separating water from raw Olimulsion. Table 2 gives the gas composition and higher and lower heating values (wet) of the fuel gases obtained by gasifying these materials. TABLE 1 Dehydrated Composition wt % Olimulsion Olimulsion Carbon 59.83 83.06 Hydrogen 7.48 10.38 Oxygen 0.20 0.28 Nitrogen 0.50 0.69 Sulfur 2.69 3.74 Ash 0.25 0.35 Water 29.05 1.50 Total 100.0 100.0 Higher heating 7113 9875 value HHV(kcal/kg)

[0060] TABLE 2 Dehydrated Gas composition Olimulsion Olimulsion vol % gasified fuel gasified fuel Hydrogen 36.404 38.407 Oxygen 0.000 0.000 Nitrogen & 0.729 0.856 ammonia Water 13.717 3.064 Carbon monoxide 43.143 55.014 Carbon dioxide 4.437 0.820 Argon 0.762 0.894 Methane 0.005 0.002 Hydrogen sulfide 0.683 0.803 Carbonyl sulfide 0.120 0.140 Sulfur dioxide 0.000 0.000 Total 100.00 100.00 Specific weight 0.8056 0.8054 (kg/Nm³) Higher heating 2460 2887 value HHV(kcal/kg) Lower heating 2286 2703 value LHV(kcal/kg)

[0061] As seen from this result, the gasified fuel obtained from hydrated Olimulsion has a low water content and a high heating value.

[0062] The above description of the present invention has been an explanation of embodiments in the case of Olimulsion, but the present invention is not limited to the case of Olimulsion. The present invention can, needless to say, be applied to all liquid fuels from super-heavy oil which must be made a flowable liquid by adding water because it generally has high viscosity. The above description has been given regarding super-heavy oil of an API Baume degree below 10, but the raw fuel in the present invention includes one with an API Baume degree of 10 to 20, which is called a heavy oil.

[0063] Also, one embodiment of another invention will be described with reference to FIG. 3. In this embodiment, the invention was carried out by using the aforementioned heat recovery apparatus shown in FIG. 3.

[0064] Olimulsion containing 29% water was used as a raw fuel. The following tables 3 and 4 give the composition, temperature, etc. of gasified fuel obtained by partial oxidation using oxygen. TABLE 3 Fluid 15 16 17 18 19 Composition Temperature 450 450 300 300 70 ° C. Pressure 26.0 25.5 25.3 25.0 24.8 atm H₂ (vol %) 37.0 37.0 37.0 37.0 42.3 CO 43.4 43.4 43.4 43.4 49.7 CO₂ 4.4 4.4 4.4 4.4 5.0 H₂O 13.7 13.7 13.7 13.7 1.3 H₂S 0.7 0.7 0.7 0.8 0.9 COS 0.1 0.1 0.1 5 ppm 5 ppm N₂ 0.7 0.7 0.7 0.7 0.8 O₂ 0.0 0.0 0.0 0.0 0.0 Total (vol %) 100 100 100.0 100.0 100.0

[0065] TABLE 4 Fluid 20 21 22 23 24 Composition Temper- 40 40 240 390 40 ature ° C. Pressure 24.6 24.0 23.8 23.6 24.0 atm H₂ (vol %) 42.0 43.1 37.9 37.9 37.9 CO 50.2 50.7 44.4 44.4 44.4 CO₂ 5.1 5.1 4.5 4.5 4.5 H₂O 0.3 0.3 12.4 12.4 12.4 H₂S 0.9 15 ppm 15 ppm 15 ppm 15 ppm COS 5 ppm  5 ppm  5 ppm  5 ppm  5 ppm N₂ 0.8 0.8 0.7 0.7 0.7 O₂ 0.0 0.1 0.1 0.1 0.1 Total (vol %) 100 100 100.0 100.0 100.0

[0066] As shown in FIG. 3, the heat recovery apparatus in accordance with this embodiment comprises a raw fuel gasifying device 1, a dust removing device 2 connected sequentially to the raw fuel gasifying device 1, a heat exchanger 3 before reduction of carbonyl sulfide, a carbonyl sulfide reducing device 4, a saturator 5, a cooling device 6 before desulfurization, a desulfurizing device 7, and a gas turbine 8 connected to the heat exchanger 3 before reduction of carbonyl sulfide, and is configured so that the desulfurizing device 7 is connected to the saturator 5 and cooling water from the cooling device 6 before desulfurization is supplied to the top of the saturator 5 by a pump 9. Reference numerals 15 to 24 in FIG. 3 denote fluids having a composition given in Tables 3 and 4.

[0067] Accordingly, by the heat exchange in the saturator 5, the gasified fuel 18 (300° C., water content 13.7 vol %) before desulfurization is heat-recovered as the desulfurized gasified fuel 22 (240° C., water content 12.4 vol %) in spite of desulfurizing operation at a low temperature. 

What is claimed is:
 1. A method for heat recovery in manufacturing gasified fuel, comprising: (a) partially oxidizing a raw fuel containing water vapor and sulfur compounds to produce a partially oxidized gasified fuel; (b) condensing water from the partially oxidized gasified fuel by passing the partially oxidized gasified fuel through a saturator to produce a partially dry gasified fuel, wherein the partially dry gasified fuel is cooled to a temperature below condensation temperature of water; (c) transferring the partially dry gasified fuel to a cooling device; (d) further condensing water from the partially dry gasified fuel via the cooling device to produce a cool dry gasified fuel; and (e) recycling the condensed water from the cooling device to the saturator to allow for heat recovery.
 2. The method for heat recovery in manufacturing gasified fuel according to claim 1, wherein the water content of the partially oxidized gasified fuel is 2 to 20% by volume.
 3. The method for heat recovery in manufacturing gasified fuel according to claim 1, further comprising: (f) desulfurizing the cool dry gasified fuel; and (g) heating and adding moisture to the cool dry gasified fuel by passing the cool dry gasified fuel through the saturator.
 4. The method for heat recovery in manufacturing gasified fuel according to claim 1, wherein the saturator is a tube type heat exchanger.
 5. The method for heat recovery in manufacturing gasified fuel according to claim 1, wherein the partially oxidized gasified fuel also contains carbonyl sulfide, further comprising contact reducing the carbonyl sulfide within the partially oxidized gasified fuel into hydrogen sulfide prior to condensing water from the partially oxidized gasified fuel.
 6. The method for heat recovery in manufacturing gasified fuel according to claim 3, wherein (f) further comprises contacting the cool dry gasified fuel with an absorbent.
 7. The method for heat recovery in manufacturing gasified fuel according to claim 3, wherein (d) further comprises cooling the partially dry gasifed fuel to a temperature between 30° C. and 60° C.
 8. The method for heat recovery in manufacturing gasified fuel according to claim 1, further comprising removing dust from the partially oxidized gasified fuel. 